PARIS – Prasugrel proved superior to ticagrelor in patients with acute coronary syndrome (ACS) in what was hailed as “a landmark study” presented at the annual congress of the European Society of Cardiology.
The results of ISAR-REACT 5 (Intracoronary Stenting and Antithrombotic Regimen: Rapid Early Action for Coronary Treatment 5) were unequivocal: “In ACS patients with or without ST-segment elevation, treatment with prasugrel as compared with ticagrelor significantly reduced the composite rate of death, myocardial infarction, or stroke at 1 year without an increase in major bleeding,” declared first author Stephanie Schuepke, MD, a cardiologist at the German Heart Center in Munich.
The study outcome was totally unexpected. Indeed, the result didn’t merely turn heads, it no doubt caused numerous wrenched necks caused by strenuous double-takes on the part of interventional cardiologists at the congress. That’s because, even though both ticagrelor and prasugrel enjoy a class I recommendation for use in ACS in the ESC guidelines, it has been widely assumed – based on previous evidence plus the fact that ticagrelor is the more potent platelet inhibitor – that ticagrelor is the superior drug in this setting. It turns out, however, that those earlier studies weren’t germane to the issue directly addressed in ISAR-REACT 5, the first-ever direct head-to-head comparison of the two potent P2Y12 inhibitors in the setting of ACS with a planned invasive strategy.
“Obviously, very surprising results,” commented Roxana Mehran, MD, professor of medicine and director of interventional cardiology research and clinical trials at the Icahn School of Medicine at Mount Sinai, New York, who cochaired a press conference where Dr. Schuepke shared the study findings.
“We were surprised as well,” confessed Dr. Schuepke. “We assumed that ticagrelor is superior to prasugrel in terms of clinical outcomes in patients with ACS with a planned invasive strategy. But the results show us that the opposite is true.”
ISAR-REACT 5 was an open-label, investigator-initiated randomized trial conducted at 23 centers in Germany and Italy. It included 4,018 participants with ST-elevation segment MI (STEMI), without STEMI, or with unstable angina, all with scheduled coronary angiography. Participants were randomized to ticagrelor or prasugrel and were expected to remain on their assigned potent antiplatelet agent plus aspirin for 1 year of dual-antiplatelet therapy.
The primary outcome was the composite of death, MI, or stroke at 1 year of follow-up. This endpoint occurred in 9.3% of the ticagrelor group and 6.9% of patients in the prasugrel group, for a highly significant 36% increased relative risk in the ticagrelor-treated patients. Prasugrel had a numeric advantage in each of the individual components of the endpoint: the 1-year rate of all-cause mortality was 4.5% with ticagrelor versus 3.7% with prasugrel; for MI, the incidence was 4.8% with ticagrelor and 3.0% with prasugrel, a statistically significant difference; and for stroke, 1.1% versus 1.0%.
Major bleeding as defined by the Bleeding Academic Research Consortium scale occurred in 5.4% of patients in the ticagrelor arm, and was similar at 4.8% in the prasugrel group, Dr. Schuepke continued.
Definite or probable stent thrombosis occurred in 1.3% of the ticagrelor group and 1.0% of patients assigned to prasugrel.
The mechanism for prasugrel’s superior results is unclear, she said. Possibilities include the fact that it’s a once-daily drug, compared with twice-daily ticagrelor, which could affect adherence; a differential profile in terms of drug interactions; and prasugrel’s reversibility of action and capacity for step-down dosing in patients at high bleeding risk.